Is it ok to take 18 months baby on short 3 days tour? What should I pack for him?

Hey, Yes, it is perfect. 18 month old child can travel well. We took our 2 month old baby to an interior place in Himachal and that too in snow. So, I do not think there should be any problem if you carry all the essential things with you. Take the basic medicines for cold, colic and fever. Medicine for earache too. Since, he is 18 months old, you will get everything that he would need to eat anywhere in the hotel or elsewhere. But you can take biscuit and grinded nuts while travelling.